The overall goal of the research is to develop clinically useful tools for the measurement of visual acuity in infants, and to identify groups of infants who could benefit from early assessment of visual acuity. Two tools that have been developed for clinical assessment of visual acuity in infants are the diagnostic grating procedure (Dobson 1983) and the acuity card procedure (McDonald et al. 1985). The present proposal will continue validation of these two procedures, and will document the natural history of acuity development in infants who experienced perinatal complications that put them at risk for acuity deficits. Research to be conducted includes: 1. Analysis of refractive error data, and acuity data obtained with the diagnostic grating procedure, in a longitudinal study of normal infants and infants with strabismus, high hyperopia, and/or a family history of strabismus or amblyopia. 2. Use of non-sequentially ordered acuity cards to test 2-, 4-, 12-, and 30-month old normal infants. This study will determine (a) the upper and lower asymptotes and the slope of the psychometric function underlying the acuity card procedure, and (b) the shift in acuity scores obtained when an observer is instructed to use a strict vs a lax criterion for judging whether an infant can see a grating, and (c) the ability of observers to use acuity cards under conditions that minimize the usefulness of a priori information. 3. Determination of interobserver test-retest reliabilities in acuity card results of normal infants and infants at risk for visual and/or neurological abnormalities, tested at due date and at 4, 9, 12, and 18 months from due date. 4. Evaluation of acuity card results in infants with perinatal complications, tested longitudinally. This study will allow us (a) to evaluate the predictive validity of early acuity testing, and (b) to determine whether infants with perinatal complications known to lead to anatomical changes in the eye and/or the central visual pathways show early visual acuity deficits.